Compressor and vacuum pump



Jan. 31, 1933. c. FFEIFFER COMPRESSOR AND VACUUM PUMP Filed April 15, 1930 2 Sheets-Sheet l Q Q a m ww &/ \V AI x Q a m v Q R vs %m m\ KN 3 MM. AM. km 3. N Y Q I \w a E 3 mm mm m 9 w NKWN INVENTOR Cesar P1 61 f/er 76) Zn4 v 1 ATTORNEYS Jan. 31, 1933. c. PFEIFFER v 1,895,816

COMPRESSOR AND VACUUM PUMP Filed April 15, 1950 2 Sheets-Sheet 2 INVENTOR Cesar PAH/fem ATTORN EYS Patented Jan. 31 1933 UNITED STATES PATENT OFFlCE ofisan rrmrrna, or'asnmnns, amen assrenon 'ro FULLER comm, A onroaarron or nnnawm COMPRESSOR AND VACUUM PUMP Application filed April 15,

This invention relates to multiple stage rotary compressors and vacuum pumps for air or other gases, and will be described hereinafter as an air compressor to simplify the description. It has particularly to do with the type of compressor of which each stage comprlses a stator casing having a substantially cylindrical bore in which a cylindrical rotor is arranged eccentrically, the rotor being provided with vanes to pocket the air in cells, to compress the air by the decrease in volume of the cells as they move toward the discharge outlet of the stage. The invention is especially directed to a compact, multiple stage rotary compressor of unitary construction in which the air, during its passage between stages, and the working parts are adequately cooled by water or other heat absorbing fluid.

The invention contemplates the combination of two or more compressor sta es supported on an elongated, hollow base forming an intercooler and air reservoir, between the low and high pressure stages. For simplicity in description the apparatus will be described as a two-stage air compressor but it is to be understood that other gases may be compressed and that it may be used as a vacuum ump. More than two stages may be assem led as a part of asingle unit.' The inner rotor shafts of the stages are directly connected through a flexible coupling and the rotors are preferably driven by a prime mover through a con 1mg on an externalrotor shaft. The air ischarging from the low pressure stage is directed downwardly and into the hollow base wherein it passes in a sinuous course around heat absorbing surfaces, preferably water carryin tubes, and then discharges into the inlet of t e high pressure stage. In the hi h pressure stage it is compressed to the desired working press'urel The water carrying tubes of the intercooler, the baflies and water headers are constructed as a unit in order that the may be removed for repair or replacement y breaking the external connections and removing one of the end plates which closes each end of the hollow base. The surface area of these tubes should be-great enough to cool the air 1930. Serial No. 444,448.

dischar ed from the low pressure stage sufliciently or the high pressure stage to o erate with favorable volumetric efliciency, t is intercooler arrangement being of especial advantage as the total heat absorbin surface area can be inclosed within a base 0 relatively small cross sectional area.

The stator casings are formed with hollow walls surrounding a large area of the bore to form water jackets interrupted only by the necessary thickness of metal to form supporting webs and to inclose the air intake and outlet of each casing.' The hollow walls are also interrupted by bafiles in the form of horizontal webs on each side of the casing at approximately the level of the center line of the casing. These baflles divide the walls into upper and lower water jackets and divert the water through jackets in the cylinder heads. Each cylinder head is provided with water jackets of substantial volume, limited b the necessary thickness of metal require for structural strength and the oil ducts. The inner face of each head is provided with a circular series of openings which connect with the upper and lower water jackets of the stator casings.

I have discovered that the most favorable circulation for the cooling water to obtain the best heat transfer for a given quantity of water is as follows: The entire volume of the water is admitted to the manifold of the intercooler at the air discharge end of the intercooler and passes through the tubes in counterflow with the air and then passes through a suitable connection into the lowermost part of the water jacket of the low pressure stage. Within the lower water jacket of the low stage, the water passes upwardly around the walls of the bore and is diverted by the baflles through each cylinder head and is combined and discharged at a central point at the top of the casing. This discharge is connected through suitable piping to t e lowermost portion of the water jacket of the high pressure stage through which it passes in a similar manner.

Although the preferred water circulatory system is described above, it is to be understood that the required volume of water can be divided and predetermined quantities delivered separately to each stage and the intercooler, or divided and one part delivered to both stages and the remainder to the intercooler without departing from the broader aspects of my invention.

In accordancewith my invention, the ad'- vantages in high volumetric eflicieney of two stage compressors and vacuum pumps with inter-coolers are obtained in a compact, unitary structure of simple construction and few parts. The device is particularly adaptable to installations where limited space would preclude the use of two stage machines of usual construction. It also has an advantage as a part of a portable compressor assembly, as its small size permits the compression of air in two stages with the corresponding high volumetric efficiency in contrast to the usual single stage compressor of low volumetric efliciency at high pressures.

For a better understanding of my invention, reference is made to the accompanying drawings in which Fig. 1 is a sectional side elevation;

Fig. 2 is a cross sectional elevation on line 2-2 of Fig. 1;

Fig. 3 is an end elevation of the base castin%with the end plate removed;

ig. 4 is an enlarged view of the inner face of one of the left cylinder heads; and

Fig. 5 is a plan view of the base shown partly broken to show the heat absorbing surfaces.

Referring to the drawings, the apparatus is shown to consist of a low pressure stage 10 and a high pressure stage 11 mounted upon a hollow, elongated base 12. This base may rest upon any suitable foundation such as that shown at 13. The stages are identical in design except for size, as the low pressure stage is larger to handle a greater volume of air. Each sta e comprises a stator casing 14 having a hollow, substantially cylindrical bore 16, a cylindrical rotor 17, arranged eccentrically within the bore 16 and formed with integral stub shafts 18 and 19 mounted in rigid roller bearings 20 and 21 in cylinder heads 22 and 23. Each stator casing 14 is provided with an air inlet 24 and an outlet 25 opening .into the bore 16.

in which thin vanes 27 are arranged to slide freely. The vanes 27 move outwardly by centrifugal force into contact with the wall of the bore 16. Between the inlet 24 and the outlet 25, which forms the working zone of the compressor, the vanes form cells which trap the air at the inlet side and compress it by progressive decrease in volume during movement toward the outlet 25. The outlet 25 is provided with any suitable non-return valve 28.

Thelower portion of the stator casing 14 of the high pressure stage is provided with an extension 29 rigidly secured to an abutbase 12, the extension 29 being longer than the corresponding extension 31 of the low pressure stage in order to align the rotor shafts of both stages, whereby the shaft 21 of the high pressure stage and the shaft 20 of the lowpressure stage can be arranged for a common drive by means of a flexible coupling 32.

The shaft 19 of the low pressure cylinder is extended as shown at 33 similarly to the end of the shaft 21 of the high pressure cylmder in order that it may be connected through a coupling to any prime mover of suitable speed.

Each stator casing 14 is provided with hollow walls 34 entirely surrounding the bore- 16 excepting for the necessary thicknessof metal to inclose the inletopening 24 and the outlet openings 25, and horizontal, central webs 35 shown in dotted lines in Fig. 2. The function of these webs 35 is to divide the hollow walls 34 into upper and lower water jackets, the water being admitted at a low point into the extensions 29 and 31. The cylinder heads 22 and 23 are similar, a cylinder head 22 being shown in detail in Fig. 4.

Each cylinder head is provided with hollow 9 per water jacket. Each of the water jackets 34 discharge through connections 39 at the center and highest point of each casing 14.

The compressed air outlet 25 of the low pressure stage has a connection 40 .(Fig. 2) opening into the base 12 near one end. The base is provided with an outlet 41 to connect with the inlet of the high pressure stage.

The base surrounds a plurality of spaced water carrying tubes, the adjacent rows be ing staggered as indicated in Fig.2. The tubes terminate at each end in tube sheets 43, which are closed by manifolds 44 to, form Water headers. The interior of the base 12 is divided by transverse baffles 45, through which the tubes 42 are passed. The baffles 45 conform to the cross section of the interior of the base 12 and alternate from side to side as indicated in Fig. 5, beginning near the connection 40.

The base .is closed at each end by removable end plates 46 through which water connections 47 and 48 are passed. The tubes 42, baffles 45 and the headers are removable as a unit by breaking the water connections, as by the union 49.

The preferred water circulation to cool the air between the outlet connection 40 of the low pressure stage and the inlet connection 41 to the high pressure stage, during the travel of the air in its sinuous course around the battles, as well as circulation to cool ,the working parts is as follows: "Water from a suitable source under pressure as'from'a water main, is admitted to the connection 47 and passes into the tubes 42' forming the intercooler and flows in the direction of the arrows in counterfiow to the air which passes around the tubes. The tubes of the intercooler discharge through the connection 48 which opens into the lowermost part of the water jacket 34 of the low pressure stage, the water entering a low point in the extension 31. The water passing around the wall of the 'bore 16 is divided and diverted through the lower openings 38 of the cylinder heads 22 and 23 and passes into the upper water jacket of the casing 14 to the upper openings 38 in the cylinder head. In the upper water jacket it is recombined and discharged through the outlet connection 39.

The outlet 39 is connected by suitable piping 50 to the Waterjackets of the high pressure stage at a low point in the casing extension 29, the connections and water flow being indicated by the arrows. The water then passes through the water jackets of the high pressure stage 11 as in the water jackets of the low pressure stage and discharges from the apparatus through the outlet 39 of the high pressure stage.

By this arrangement I am able to reduce the temperature of the air discharged from the low pressure stage sufficientlj so that the high pressure stage can operate at high volu metric efiiciency and to cool all working parts adequately with a minimum quantity of water and with few water connections.

I claim:

A multiple stage rotary compressor comprising the combination of a low pressure stage, a high pressure stage, an elongated hollow base upon which the stages are mounted, each stage comprising a stator casing having a central bore, a cylindrical rotor provided with a shaft mounted for rotation in end thereof and water carrying tubes ar-.

ranged within the base provided with transverse air baffles to cause the air to describe a sinuous course through the base in counter flow to the water in the tubes to cool the air between compressor stages, interconnected water jackets on the compressor stages, and connections between the discharge ends of the water tubes and the low pressure stage water jacket.

In testimony whereof I afix my signature.

CESAR PFEIFFER. 

